The present invention relates to a film forming composition, a process for producing a film forming composition, an insulating film forming material, a process for forming a film, and a silica-based film. More particularly, the present invention relates to a process for producing a film forming composition which can form a film having a low relative dielectric constant and exhibiting excellent chemical resistance, adhesion, and insulating properties, a film forming composition, an insulating film forming material, a process for forming a film, and a silica-based film.
Conventionally, a silica (SiO2) film formed by a vacuum process such as a CVD process has been widely used as an interlayer dielectric in a semiconductor device or the like. In recent years, a spin on glass (SOG) film which is a coating type insulating film containing a tetraalkoxysilane hydrolyzate as a major component has been used in order to form a more uniform interlayer dielectric. Accompanied by an increase in the degree of integration of a semiconductor device or the like, a low-relative-dielectric-constant interlayer dielectric called an organic SOG containing organopolysiloxane as a major component has been developed.
However, since an increase in the degree of integration of a semiconductor device or the like has further progressed, further excellent electrical insulation between conductors has been demanded. Therefore, an interlayer dielectric material having a lower relative dielectric constant has been in demand.
To deal with this demand, coating type insulating film forming compositions having a lower relative dielectric constant have been disclosed as interlayer dielectric materials (see Japanese Patent Application Laid-open No. 6-181201, Japanese Patent Application Laid-open No. 2000-256621, and Japanese Patent Application Laid-open No. 2002-285086, for example). The coating type composition disclosed in Japanese Patent Application Laid-open No. 6-181201 aims at providing an insulating film for a semiconductor device having low hygroscopicity and excellent cracking resistance. This coating type insulating film forming composition contains, as a major component, an oligomer with a number average molecular weight of 500 or more which is obtained by polycondensation of an organometallic compound containing at least one element selected from titanium, zirconium, niobium, and tantalum and an organosilicon compound having at least one alkoxy group in the molecule.
The film forming compositions disclosed in Japanese Patent Application Laid-open No. 2000-256621 and Japanese Patent Application Laid-open No. 2002-285086 are obtained by hydrolyzing and condensing alkoxysilanes in the presence of a metal catalyst. The film forming composition disclosed in Japanese Patent Application Laid-open No. 2000-256621 has a low relative dielectric constant and a high modulus of elasticity and excels in cracking resistance and CMP resistance. The film forming composition disclosed in Japanese Patent Application Laid-open No. 2002-285086 has a low relative dielectric constant and low hygroscopicity, excels in film uniformity, and causes an increase in film thickness to only a small extent during long-term storage.
In the semiconductor device manufacturing process in recent years, a chemical mechanical polishing (CMP) step has been widely used in order to plarnarize a stacked film. Therefore, adhesion between the interlayer dielectric and the substrate is demanded for a semiconductor device so as to withstand the CMP step.
In the semiconductor device manufacturing process, a washing step is generally performed after performing etching and ashing steps. Chemicals such as hydrofluoric acid are used in the washing step. Chemicals such as hydrofluoric acid may be used as an etchant for wet etching. In the case of an insulating film formed by using a conventional film forming composition, the contact surface with the above chemical used in the washing step or the etching step is eroded, whereby insulating properties may be decreased. Even if the contact surface with the chemical is not eroded, the surface of the insulating film undergoes chemical changes and absorbs water, whereby the insulating properties may be decreased. Therefore, formation of an insulating film having adhesion and chemical resistance which can withstand the CMP step and having insulating properties is demanded.